Learn how to create flexible schemas in a relational database using SQL for JSON.

The Dropbox blog has an excellent post for anyone using MongoDB on a large scale. The startup, Mailbox, spent a lot of time making their own set of tools after discovering that the cloneCollection and renameCollection commands built into MongoDB weren't going to help them meet their scaling and performance reads, which they ran into often was MongoDB's database-level write lock.

The tools they created, dubbed "Hydra," have been open sourced on GitHub. You should definitely read this post if you want to get an idea of how some really awesome developers solved some very tricky scalability problems in their MongoDB deployment.